Process for recovery of noble metals from functionalised, noble metal-containing adsorption materials

Abstract

A method recovers noble metals from noble metal-containing compositions and includes steps of (i) providing a noble metal-containing composition containing an adsorption agent that is based on an inorganic material and is functionalized by organic groups and has at least one noble metal adsorbed to it, and (ii) ashing of the noble metal-containing composition provided in step (i) in order to adjust a residual carbon content of at most 10% by weight, relative to the total weight of the noble metal-containing composition after ashing, to obtain an ashed composition.

The invention claimed is: 
     
       1. A method for recovery of noble metals from noble metal-containing compositions, the method comprising the steps of:
 i) providing a noble metal-containing composition containing an adsorption agent, comprising an inorganic material and functionalized by organic groups; and having at least one noble metal adsorbed to the absorption agent; 
 ii) ashing of the noble metal-containing composition to adjust a residual carbon content to at most 10% by weight, relative to the total weight of the noble metal-containing composition after ashing, to obtain an ashed composition; 
 iii) at least partial dissolution of the ashed composition in an alkaline aqueous solution to obtain a noble metal-containing residue; 
 iv) at least partial dissolution of the noble metal-containing residue in an oxidizing aqueous acid to obtain an aqueous salt solution of the noble metal; and 
 v) optionally, recovering the noble metal through reduction of the noble metal salt solution. 
 
     
     
       2. The method according to  claim 1 , wherein the adsorption agent is a silica gel- or an aluminium oxide gel-based adsorption agent. 
     
     
       3. The method according to  claim 1 , wherein the adsorption agent is functionalized by 0.1 to 1.5 mmol/g organic groups. 
     
     
       4. The method according to  claim 1 , wherein the noble metal-containing composition contains at least 0.5% by weight of noble metal, relative to the total weight of the noble metal-containing composition. 
     
     
       5. The method according to  claim 1 , wherein the noble metal-containing composition is obtained by contacting a noble metal-containing residue and an adsorption agent that is functionalized by organic groups and based on an inorganic material. 
     
     
       6. The method according to  claim 1 , wherein the ashing of the noble metal-containing composition proceeds at a temperature above 700° C. 
     
     
       7. The method according to  claim 6 , wherein the ashing of the noble metal-containing composition proceeds for a period of time of at least two hours. 
     
     
       8. The method according to  claim 1 , wherein the at least partial dissolution of the ashed composition in an alkaline aqueous solution to obtain a noble metal-containing residue proceeds in the presence of a reducing agent. 
     
     
       9. The method according to  claim 8 , wherein the reducing agent is an organic reducing agent, hydrazine or hydrogen gas. 
     
     
       10. The method according to  claim 9 , wherein the organic reducing agent is selected from the group consisting of formic acid, a formic acid salt, formaldehyde, alcohols, ascorbic acid, glucose, gluconic acid, and oxalic acid. 
     
     
       11. The method according to  claim 1 , wherein the noble metal-containing residue is reduced in a hydrogen stream prior to step iv). 
     
     
       12. The method according to  claim 1 , wherein the noble metal-containing residue loses by more than 90% total mass as compared to the material in step i). 
     
     
       13. The method according to  claim 12 , wherein the loss of total mass exceeds 95%. 
     
     
       14. The method according to  claim 1 , wherein the at least partial dissolution of the noble metal-containing residue in an oxidizing aqueous acid to obtain an aqueous salt solution of the noble metal proceeds in nitric acid, in a mixture containing hydrochloric acid and nitric acid, in hydrochloric acid containing chlorine gas or in hydrochloric acid containing chlorate.